Bugfix IPv6 netloc parsing

This bug was introduced in a723b61; if IPv6 worked in the CI environment, it
would've been caught earlier... but it didn't in Travis-CI, so I removed
the one IPv6 test target in 0926711.

Let's add it back and see if it works with GitHub-CI workflows?

tests/test_sniffers.py

@@ -42,12 +42,13 @@
     ('vpn.sgh.waw.pl', sn.global_protect),     # portal
     ('vpn-gw.sgh.waw.pl', sn.global_protect),  # gateway
     ('jvpn.tn.gov', sn.juniper_pulse),
-    ('174.127.47.193', sn.check_point),  # no DNS?
+    ('174.127.47.193', sn.check_point),        # no DNS?
     ('nomad.sandiego.edu', sn.aruba_via),
     ('viavpn.luther.edu', sn.aruba_via),
     ('vpn.wdc.softlayer.com', sn.array_networks),
-    ('166.111.32.74:10443', sn.h3c), # no DNS? tsinghua.edu.cn
-    ('58.246.39.91:8899', sn.huawei), # no DNS? China, non-edu
+    ('166.111.32.74:10443', sn.h3c),           # no DNS? tsinghua.edu.cn
+    ('58.246.39.91:8899', sn.huawei),          # no DNS? China, non-edu
+    ('[2620:0:e00:17::2]', sn.anyconnect)      # address changes sometimes (https://dns.google/query?name=vpn.cites.illinois.edu&type=AAA)
     ]
 
 unmatched_vpns = ['vpn.{}.edu'.format(d) for d in (
@@ -101,3 +102,16 @@ def test_unmatched_vpns(self):
         for domain in unmatched_vpns:
             shuffle(self.sniffers)
             yield self.check_hits, domain, None
+
+
+def test_server_split():
+    def check_server_split(netloc, expected):
+        assert sn.server_split(netloc) == expected
+
+    for netloc, expected in (
+        ('foo.bar.com:123', ('foo.bar.com', 123)),
+        ('foo.bar.com', ('foo.bar.com', 443)),
+        ('[dead:beef::f00f]', ('[dead:beef::f00f]', 443)),
+        ('[dead:beef::f00f]:789', ('[dead:beef::f00f]', 789)),
+    ):
+        yield check_server_split, netloc, expected

what_vpn/sniffers.py

@@ -48,7 +48,7 @@ def server_split(host_and_maybe_port):
     rest, *last = host_and_maybe_port.rsplit(':', 1)
     if not last:
         host, port = rest, 443
-    elif ']' in last:  # we mis-split an IPv6 address, something like '[2601::1234]':
+    elif ']' in last[0]:  # we mis-split an IPv6 address, something like '[2601::1234]':
         host, port = host_and_maybe_port, 443
     else:
         host, port = rest, int(last[0])